Double acting clutch



Jan. 13, 1959 Filed April l, 1957 J. B. SNOY 2,868,341 DOUBLE ACTINGCLUTCH 2 Sheets-Sheet 1 frizzerzz 'or Jan. 13, a SNOY DOUBLE ACTINGCLUTCH 2 Sheets-Sheet 2 Filed April 1, 1957 mNx NNN

h WE. wwx w w k Q Q m 3 N 1Q 1Q Q Q mm h hm mm m E b w United StatesPate has 2,868,341 DOUBLE ACTING (ILUTtCH Joseph B. Snoy, Rockford,111., assignor to Borg-Warner Corporation, Chicago, 11]., a corporationof ilillinois This invention relates to hydraulically operated clutchmechanisms, and more particularly to hydraulically operated clutchmechanisms of the type designed to operate either of a pair of opposedclutch packs.

In the copending application of Elmer A. Richards and myself, SerialNumber 593,479, filed June 25, 195(, and entitled Double HydraulicOperated Clutch Device there is disclosed and claimed a new and improvedhydraulically operated clutch mechanism which is simpler, fasteroperating and providing, nevertheless, better cushioned engagement thanany device of a comparable nature previously known to us. The presentinvention is an improvement over that described in the aforementionedcopending application.

It is one object of the present invention to provide a new and improvedhydraulically operated clutch device operable with a lower hydraulicpressure than heretofore possible while yet retaining features ofhydraulic balance, smoothness in operation and rapidity of action.

Another object of the present invention is the provision of a new andimproved hydraulically operated clutch device in which a centralreaction plate is provided having simple and inexpensive valvingmechanisms associated therewith to control transfer of hydraulic fluidfrom one compartment adjacent one side of the reaction plate to thecompartment at the opposite side of the reaction plate.

Other objects and features of the invention will be readily apparent tothose skilled in the art from the specification and appended drawingsillustrating certain preferred embodiments in which:

Figure l discloses a central longitudinal sectional view through thedevice incorporating the principles of the present invention;

Figure 2 is a partial view similar to Figure 1 illustrating a devicehaving a modified form of the present invention;

Figure 3 is a schematic diagram illustrating a circuit containingdevices of the type illustrated in Figures 1 and 2.

In Figure 1 there is disclosed a longitudinally extending, rotatableshaft 1 adapted for connection to a prime mover, such as an shown)having an elongated bore 2 extending axially therein. Disposed withinthe bore 2 is an imperforate tube 3 extending partway through the bore2, as illustrated in Figure 1, and having an outer diameter such as tobe spaced from the sides of an enlarged portion of the bore 2 to definean annular fluid channel 4 there between. In fluid communication withthe channel 4 are a plurality of circumferentially spaced, radiallyextending ports 5 extending to the exterior of the shaft 1; alsoextending from the bore 2 to the exterior of the shaft 1 are a pluralityof circumferentially spaced, radially extending ports 6 which, asdisclosed in Figure 1, are in fluid communication with the tube 3 butnot in communicat-ion with the channel 4 in View of the fact thatinternal combustion engine (not plate 8 is annular in N the exterior ofthe tube 3 is in fluid tight engagement at 7 with a reduced diameterportion of the bore 2.

Disposed upon the shaft 1 for rotation therewith is a reaction plate 8prevented from axial movement by snap rings 9, the reaction plate 8,however, having a central circular aperture therein numbered 11, thesides of which engage the exterior surface of the shaft 1 so that theplate 8 is rotatable therewith. The reaction configuration, and isprovided at its outer periphery with an annular groove 12 within whichis disposed a sealing ring 13. The sealing ring 13 is disposed inengagement with the inner surface of a generally annular piston housing14 which is imperforate so as to contain hydraulic fluid, as will bemore fully described hereinafter. It will be seen that the plate 8 ineffect divides the interior of piston housing 14 into a pair of spacedfluid chambers 15 and 16.

Mounted to the shaft 1 so as to be axially movable with respect theretois an annular piston 17. The outer periphery of the piston 17 isprovioed with a seal 18 disposed in engagement with the inner surface ofpiston housing 14 to prevent leakage of hydraulic fluid between piston17 and the piston housing. A snap ring 19 is provided in a suitablegroove in the piston housing 14 which engages the left side of piston17, in the view of Figure 1, to prevent further movement to the left ofthe piston 17. A plurality of circumferentially spaced apertures 21 areprovided which extend through an inner portion of piston 17 to providemetered cooling flow of fluid to the clutch plates, and suitable sealingmeans 22 are providedin shaft 1 between the shaft and the annularcentral opening in piston 17 to prevent fluid flow therebetween. Thepiston 17 has integrally formed therewith an inwardly extending, annularledge 23, an inner portion of which carries a snap ring 24. An annularspring 25 having an annular central opening therein seated upon theledge 23 is provided, the innermost portion of which is engaged by abracket 26 rigidly connected at one end by bolts 27 to the reaction 26engaging spring 25. The spring 25 has a plurality of spaced, radiallyextending fingers 28 which engage an inwardly facing, upper portionofthe piston 17 to bias it away from plate 8.

The radially under side of the annular ledge 23 is disposed inengagement with the radially outer surface of an annular ledge 29 of anannular accelerating piston .35, having a plurality of suitable openingsthrough which portions of the brackets 26 extend, and radially inwardlythereof is an annular surface 36 facing the reaction plate 3 and spacedtherefrom to a greater degree than the face of the radially outerportion 35 of the piston 31.

In radial registry with the portion 35 of the piston 31, are a plurality(preferably 6) of openings 37 which extend through the reaction plate 8.Each of these openings 37 is provided with a one-way valve arrangement,which reflow direction, and each of which of the reaction plate 8; eachof the one-way valves fur- Patented Jan. 13, 1959 I end thereof onlyfixedly connected, as by riveting, to the reaction plate 8 and disposedon the side of the associated opening 37 opposite to that of theassociated bushing the flapper 41 being sufficiently large in area tooverlie the entire associated opening side. As a result of thisarrangement, it will be apparent to those skilled in the art that fluidflow may normally occur in one direction through any opening 37, butflow in the opposite direction through that opening is prevented. Aspreviously indicated, and as shown in Figure 1, the one-way valves ineach of the openings 37 are respectively reversed as the openings 3? arerespectively considered circumferentially, so that alternate openingspermit flow through reaction plate 3 in opposite directions. I

Also mounted to the shaft 1 so as to be axially movable with respectthereto is an annular piston outer periphery of the piston l; isprovided W h a 48 disposed in engagement with the inner surface ofannular piston housing 14 to prevent leakage of hydraulic fluid betweenpiston 47 and the piston housing. A snap ring d9 is provided with asuitable groove in the piston housing 14 which engages the right side ofpiston 47, in the view of Figure l, to prevent further movement to theright of the piston relative the piston housing. A plurality ofcircumferentially spaced apertures Eli are provided which extend throughan inner portion of piston &7 to provide metered cooling flow of fluidto the clutch plates, and suitable sealing means 52 are provided inshaft l between the shaft and the annular central opening in piston t!to prevent fluid flow therebetween. The piston 7 has integrally formedtherewith an inwardly extending, annular ledge 53, an inner portionthereof carrying a snap ring 54. An annular spring 55 is provided whichhas an annular central opening therein seated upon the ledge theinnermost portion of the spring 55 being engaged by a bracket d, similarto the bracket 26, rigidly connected at one end by bolts 2'7 to thereaction plate 0, the opposite end of bracket 56 engaging the spring 55.The spring has a plurality of spaced, radially extending lingers whichengage an inwardly facing, upper portion of the piston 47 and tend tobias it toward the right in the view of Figure l.

The radially under side of the annular ledge 53 is disposed inengagement with the radially outer surface of an annular ledge 59integrally formed on an annular accelerating piston 62. Suitable sealingmeans 62 are provided between the ledges 53 and 59 to prevent fluid flowtherebetween. The piston 61 has a central, circular aperture disposedtherein in contact with the outer periphery of the shaft 1, piston 61being axially movable, however, relative to the shaft 1. Sealing means63 are provided which prevent fluid flow between the shaft l and piston61. The ledge 59 of piston 61 has opening means 64 extendingtherethrough to provide restricted fluid communication between thechambers at the radially opposite sides of the ledge 59. The radiallyextending portion of the piston 61 comprises a radially outer annularportion 65, having a plurality of suitable openings through whichportions of the brackets 56 extend, as illustrated in Figure l, andradially inwardly thereof is an annular surface 66 facing the reactionplate 5 and spaced therefrom to a greater degree than the face of theradially outer portion 65' of the piston From the foregoing descriptionit will be seen that the piston housing the pistons 17 and 4/7, thereaction plate 8, the pistons 31 and 61 define fluid chain ers l5 and lowithin the piston housing 1 which normally are in fluid communicationthrough the one-way valves in the openings 37 in the reaction plate Inaddition, radially inwardly of the chamber another annular iiluidchamber is formed by the outer surface of shaft 1, an annular surface'75 integral with the piston '17, the radially inner .portion of ledges23 and 29, and an annular surface 77 on piston 31. Chamber "i5 is. in

fluid communication at all times with the ports 6', and fluid may passout of this chamber through the restricted apertures 21, and alsothrough the restricted opening Y and 5), and an annular surface till onpiston 61. Chamber 78 is in fluid communication at all times with thenorts fluid may flow out of the chamber 7 8 through the ted apertures 5iin the piston 47, and also through the restricted opening means 64 inthe ledge 59.

Splined from the shaft 1 at opposite sides of the aforedescribedcylinder assembly are clutch hubs Sll and 82 respectively which aregenerally annular in coufigura lion. Hub 31 is prevented from axialmovement along the shaft 1 by snap rings 83 and 84, while hub 82 isprevented from axial movement along the shaft 1 by similar snap rings 85and S6. The outer periphery of hub 51 has integrally formed thereonsplines 87 which engage complementary splines on clutch plates 88 whichare interleaved with other clutch plates 89, the latter being splined toan annular cup-shaped clutch drum 91. Also mounted upon the hub 81 areclutch backing means E li fixed against axial movement to the left, inthe view of Figure l, by a snap ring 93. A retainer plate Q4 is fixed tothe innermost facing portion of hub 81 which has an inwardly directedportion which serves to direct fluid flowing through the apertures 21toward a plurality of suitable holes id in the hub 81 and there foreinto engagement with the clutch plates 38-and 89.

in similar fashion, in splined engagement with the outermost surface ofthe hub 82 are a plurality of clutch plates 97 intermeshed with aplurality of clutch plates splined to a cup-shaped clutch drum. 9. Alsomounted on the hub 82 is a backing plate till fixed against movement tothe right in the view of Figure l, by a snap ring W2. A retainer plate103 is mounted to the inwardly facing portion of hub 82, plate ill 3having an inwardly directed portion ltld which serves to direct fluidflowing through the apertures :31 into engagement with the clutch plates97 and '93 through a plurality of suitable holes 1% in the hub 32.

It will therefore be seen that the intermeshing clutch plates 83 and 39form a clutch pack indicated in general by the numeral 1%, while theintermeshing clutch plates 97 and 98 form a clutch pack indicated ingeneral by the numeral 107.

The clutch drum 91 is fixedly mounted by means of rivets 1% to a gear169, rotatably mounted on the shaft 1, and intermeshing with othergearing 111 (Figure 3 the clutch drum 9) is fixedly mounted, such asSimilarly, by rivets 12, to a gear 113 rotatably mounted about the theshaft 1 and intermeshing with other gearing 114 (Figure 3).

it will be obvious to those skilled in the art that in the conditionillustrated in Figure 1, neither the gear 109 nor the gear M3 will bedriven from the shaft 1. When the clutch pack lilo, however, is engaged,rotative power will be transmitted from the shaft 1 to the gear ill"?and the gearing ill. Similarly, when the clutch pack 1&7 is engagedrotative power will be transmitted from the shaft 1 to the gear 113 andthe gearing 1114.

In Figure 3 these is shown schematically an operative system employingthe device of the present invention. in that figure shaft l isillustrated carrying the clutch packs and M97, the piston housing i l,and the other elements therein previously described. Gear ll l is shownin meshing relation with gearing ill, the latter being mounted upon asuitable countershaft 115 so that upon engagement of the clutch pack 1%,power is transmitted from the engine, through the shaft 1, the clutchpack gear 16?, gearing 111 and countershaft 1515 which is attached bysuitable means to the drive wheels of the vehicle (not shown).Similarly, upon engagement of the cation with a regulator valve 135clutch pack 107power will flow from the engine to the shaft 1, clutchpack 107, gear 113, gearing 114 to the countershaft 115, and from thecountershaft 115 to the driving wheels of the vehicle. Obviously thegear ratio between the gear 109 and the gearing 111 is different thanthe ratio between the gear 113 and the gearing 114 so that the shaft 115will be driven at one speed when the clutch pack 106 is engaged and at adifferent speed when the clutch pack 107 is engaged. It will also beapparent that an idler gear can be interposedbetween the gearsillustrated so that a reverse drive may be accomplished by engagement ofa suitable clutch pack.

To supply hydraulic fluid to the piston housing 14, as shown in Figure3, the shaft 1 is provided with radially extending ports 116 in fluidcommunication with the channel 4 (formed in the shaft 1 between theperiphery of the bore 2 therein and the tube 3). The ports 116 are influid communication with hydraulic fluid carrying means 1.17. Similarly,hydraulic fluid carrying means 118 are provided which are in fluidcommunication with the tube 3, the hydraulic fluid carrying means 117and 118 being hydraulically isolated from each other. The fluid carryingmeans 117 and 118 are respectively connected to a selector valve 119,which is supplied by a high pressure fluid carrying line 121 and a lowpressure fluid carrying line 122. The selector valve 119 may be ofconventional type which, when in one position, will permit fluid flowfrom the low pressure line 122 to both of the fluid carrying means 117and 118 simultaneously; when the selector valve 119 is placed in adifferent position, the low pressure line will be connected to one ofthe fluid carrying means 117 or 118, and the high pressure line 121 willbe connected to the other of these fluid carrying means. In anotherposition of the selector valve 119, the opposite fluid carrying meanswill be connected to the high pressure line while the other fluidcarrying means will be connected to the low pressure line.

The lines 121 and 122 are supplied with hydraulic fluid from a suitablepump 123 in fluid communication with a sump 124. The pump 123 delivershigh pressure fluid to a line 125 which is in turn connected to thejunction between the high pressure line 121 and a line 126, the latterbeing in fluid communication with a regu lator valve 127 of conventionaldesign adapted to maintain the pressure in line 121 at a desired level.The regulator valve 127 is in turn connected to a hydraulic line 123which carries fluid to a torque converter 129 of the vehicle in whichthe device incorporating the present invention is disposed, theconverter having an output hydraulic line 131. Line 131 is connected toa cooler 132, through which the hydraulic fluid flows to a line 133which is in fluid communication with the low pressure line 122 and aline 134, the latter being in fluid communiof conventional type adaptedto maintain the pressure in the low pressure line 122 at a predeterminedlevel. Regulator valve 135 is also connected to a fluid carrying line136 connected to the sump 124.

In the aforementioned description of the circuit illustrated in Figure3, it will be seen that hydraulic fluid under very low pressure may besimultaneously provided to the interior of tube 3 (in fluidcommunication with the ports 6) and to the channel 4 (in fluidcommunication with the ports 5). When desired, the selector valve 119may supply hydraulic fluid at a high pressure to the channel 4, andtherefore to the ports 5, while a low pressure is supplied to the tube 3and consequently to the ports 6. Conversely, the channel 4 and ports 5may be connected to the low pressure supply, while the tube 3 and ports6 are connected to the high pressure supply.

Considering now in greater detail the operation of the deviceillustrated in Figure 1, the shaft 1 is normally rotated from theengine, the hubs 81 and 82, the pistons ,17 and 4" springs 25 and 55,the pistons 31. and 61, reaction plate 53 and piston housing 14 rotatingwith the shaft 1. Hydraulic fluid at low pressure is normally constantlysupplied to the assembly through the channel 4 and the tube 3 so thatthe chambers 15, 16, '75 and are maintained full of hydraulic fluidnormally at equal pressure. Inasmuch as this pressure is equalizedthroughout these chambers and the areas acted upon by this pressure areequal, the net centrifugal effect of the rotation of this hydraulicfluid is zero. The springs 25 and 55 are preloaded so as to respectivelyapply predetermined bias to the pistons 17 and 47 and bias these pistonsto the position iliustrated in Figure 1. i

As previously indicated, under these circumstances, there is no drivetransmitted from the shaft 1 to either of the clutch packs 1116 or 1117.Assuming it is desired to effect a drive from the shaft 1 through theclutch pack 10" gear 113, and gearing 11 1 to the countershaft 115,selector valve is positioned to supply high pressure fluid to thechannel 4, while continuing to supply low pressure fluid to the tube 3.This high pressure fluid will be transmitted through the ports 5 intothe chamber 78. Piston 61 Will therefore be moved axially along theshaft 1 until the radially outer portion 65 thereof engages theassociated shoulders 39 on the adjacent bushings 38 (as illustrated inthe lower half of Figure 1). It should be noted that under thiscondition fluid flow from chamber 16 toward chamber 15 is prevented;fluid may still flow, how ever, into chamber 16 through the one-wayvalves which have the flappers :1 thereof adjacent the piston 61. Thepiston 61 does not hold these flappers 41 closed inasmuch as theshoulders 39 hold the piston 61 in a position slightly spaced from thereaction plate 8. As a result, the high pressure fluid in chamber 73will effect movement of piston 47 to the right, in the view of Figure 1,carrying the piston housing 14 with it. Chamber 15 will correspondinglyreduce in volume inasmuch as snap ring 19 will carry piston 17 to theright with the housing 14, fluid passing from chamber 15 through theplurality of openings 37 in the reaction plate 8 which contain one-wayvalves of the type illustrated in the upper portion of Figure 1. (Fluidflow through the one-way valves of the type illustrated in the lowerportion of Figure 1 is prevented inasmuch as the direction of this fluidflow is contrary to that permitted by the flappers 41 in the one-Wayvalves oriented as illustrated in that lower portion of Figure 1.) Thisflow of fluid from chamber 15 into chamber 16 obviously occurs becausethe pressure in chamber 15, which is decreasing in volume, is greaterthan that in chamber 16, which is increasing in volume. The pressure inchamber 15,'therefore, is also greater than the pressure in the chamber75, radially inwardly of the chamber .15, and connected to the lowpressure supply, this pressure differential keeping accelerating piston31 in engagement with bracket 26, as illustrated in Figure 1, so thatpiston 31 cannot inhibit the transfer of fluid from chamber 15 intochamber 16. Restated in another Way, piston 31 is held in engagementwith the bracket 26 because the chamber 75 is connected to the lowpressure source through ports 6, while chamber 15 is not so connected tothe low pressure supply; the pressure in chamber 15 will, therefore,exceed that in chamber "/5 during this movement of the assembly towardthe right in Figure 1.

When the piston 47 is moved sufliciently toward the right to engage theclutch pack 107 and supply a force thereto, further movement to theright in the assembly is momentarily stopped. The pressures in chambers15 and 16 therefore equalize almost immediately. pressure fluid inchamber 711, however, bleeds through the opening means 64 in ledge 59 ofpiston 61, passing into the chamber 16. The pressure in chamber 16 willtherefore exceed that in chamber 15 and the plurality of flappers 41oriented like that illustrated in the upper portion of Figure 1 will beforced against the reaction plate 8. As a result, all further interflowbetween chambers 15 and 16 is prevented, certain of the openings 37being blocked hy the flapper valves, while the remainder of the openingsThe high i 37 are blocked by the piston all. This increased pressure inchamber 16 effects slight further movement of piston 47 to the right inthe view of Figure l to lock up the clutch pack 107; the increasedpressure in chamber due to this movement of the assembly is bled throughthe opening defining means 3 in the ledge 29 of accelerating piston 31into the chamber 75, and out the ports 6 to the low pressure source. itshould be realized that this operation proceeds with great rapidity andsmoothness, the temporary interruption of movement of the piston 47being almost imperceptible.

With clutch pack 197 in its locked up condition, rotation of shaft 1, aspreviously described, will pass through the clutch pack to the gear 113connected thereto which, in turn, will effect rotation of gearing 114 inthe countershaft 115.

When it is desired to disengage the clutch pack 107, selector valve 11)is again returned to the position in which the passage 4 is connected tothe low pressure source. This will immediately reduce the pressure inthe chamber 73 and the spring 25, which had been stressed by movement ofthe assembly toward the right in Figure 1, will effect movement of theassembly toward the left in Figure 1. it should be noted that when thechamber 73 was connected to the low pressure source through the selectorvalve ill), the pressure in chamber 16 could not immediately return tothis low value inasmuch as the connection between chamber 16 and chamber78 is only through the restricted opening means 64. Similarly, as springbegins movement of the assembly toward the left in Figure l, thepressure in chamber 16 tends to be increased inasmuch as the volumethereof is being decreased. Despite the fact, therefore, that theaccelerator piston 51 occupies a position in engagement with thebushings 35 in the openings 3'7 when this return movement was initiated,the result of the higher pressure in chamber to than that in chamber 78will be to force immediate movement of the piston 61 into engagementwith the bracket 56, the piston 61 and bracket 56 occupying the relativepositions illustrated in Figure 1. This action is ensured by virtue ofthe fact that, as previously described, the face ss formed on piston 61is spaced from the reaction plate 3 to a greater degree than the face onportion 65 of piston til which was in engagement with the bushings 3%;as a result, the high pressure in chamber 16 is operativc against thisface es to force piston 61 away from reaction plate 3. Fluid maytherefore flow from chamber 1 .6, decreasing in volume, into chamber 15,increasing in volume, through the openings 37 having one-Way valvesoriented in the direction illustrated in the lower portion of Figure l.The assembly will continue moving toward the left until the devicereaches the condition illustrated in Figure l, at which time the biasingaction of springs 25 and 5'5 balance to hold the assembly in a neutralcondition. The clutch packs 1197 and res then, as previously described,do not transmit rotation of shaft it to the gearing associatedtherewith.

it will be obvious to those skilled in the art that engagement anddisengagement of the clutch pack 1% is efiected in a manner comparableto that described with regard to the clutch pack MP7, so a detailedexplanation of this operation will not be made.

Attention is now directed to Figure 2, which illustrates a modification.Elements bearing the same numeral in Figure 2 are identical with thoseof Figure l. The only difference between the structures illustrated inFigures 1 and 2 resides in the fact that the accelerating pistons 31 andall of Figure l are slightly modified. In Figure 2 these modifiedpistons are respectively designated 31 and or. Piston 3i is providedwith a plurality of circumferentially spaced apertures 141, each ofwhich receives one end of a spring 142, the opposite end of which abutsagainst the reaction plate 8. In similar fashion, the piston is providedwith a plurality of circumferentially spaced openings Il -t3, each ofwhich receives one lit end of a spring 144, the opposite end of whichabuts against the reaction plate 8. These springs 142 and 144 arerelatively weak, but supply a slight bias to their respective associatedaccelerating pistons which assist in moving these pistons away from thereaction plate 8 during the return movement of the assembly from eitherof its positions in which the clutch packs associated therewith arelocked up to the neutral position of the assembly.

From the foregoing description of the construction and operation of thedevices illustrated in the figures, it will be seen that they are simpleand relatively economical, and yet operate with certainty. In thisregard, it should be noted that the accelerating pistons will move toblock fiuid flow through certain of the one-way valves in the openings37 of the reaction plate 8 even though the pressure difference betweenthe high pressure and low pressure sources are relatively small. As aresult, even though through some fault in the supply system the highpressure applied to engage one of the clutch packs is at a lowerpressure level than desired, the proper clutch pack will nevertheless belocked up, without any partial slipping. in addition, the centeringmechanism is extremely simple, and does not depend on any accumulativeeffect of a plurality of springs. It should further be noted that one orthe other of the accelerating pistons is always held in its positionmost spaced from the reaction plate when any movement of the housing 14occurs, this being accomplished by and ensured by the pressuredifferentials acting upon such piston as previously described. Inaddition, simultaneous actuation of both of the clutch packs isimpossible, and the effects of centrifugal force on the oil in theclutch housing are nullified. Furthermore, inasmuch as the clutchhousing remains at all times filled with oil, extremely rapid engagementof either of the clutch packs is effected. Furthermore, as previouslynoted, the clutch operation is characterized by extreme smoothness,transfer of the high pressure from the radially inner chambers to theradially outer chambers occurring only gradually through the restrictedopening means provided in the ledges in the accelerating pistons.

While certain preferred embodiments of the invention have beenspecifically disclosed, it is understood that the invention is notlimited thereto, as many variations will be readily apparent to thoseskilled in the art and the invention is to be given its broadestpossible interpretation within the terms of the following claims.

I claim:

1. in a hydraulically operable clutch assembly, a housing, clutch means,spaced piston means movable to engage said clutch means, reaction meansdefining a plurality of first chamber means with said piston means andhousing, a plurality of one-way valve means extending between saidplurality of first chamber means, certain of said valve means preventingfluid flow in one direction only and others of said valve meanspreventing fluid flow in the opposite direction only, and other pistonmeans defining a plurality of other chamber means with said firstmentioned piston means and movable into engagement with at least certainof said one-way valve means upon the occurrence of predeterminedpressure differences between said first and other chamber means toprevent fluid fiow through said certain one-way valve means.

2. In a hydraulically operable clutch assembly, a housing, clutch means,spaced piston means movable to engage said clutch means, reaction meansdefining a plurality of first chamber means with said piston means andhousing, a plurality of one-way valve means in said reaction meansextending between said plurality of first chamber means, certain of saidvalve means preventing fluid fiow in one direction only and others ofsaid valve means preventing fluid flow in the opposite direction only,and other piston means defining a plurality of other chamber means withsaid first mentioned piston means and movable into engagement with atleast certain of said one-way valve means upon the occurrence ofpredetermined pressure diiferences between said first and other chambermeans to prevent fluid flow through said certain one-way valve means.

3. In a hydraulically operable clutch assembly, a housing, clutch means,spaced piston means movable to engage said clutch means, reaction meansdefining a plurality of first chamber means with said piston means andhousing, a plurality of opening defining means extending through saidreaction means, a plurality of one-way valve means respectively disposedin said opening defining means normally communicating said plurality offirst chamber means, certain of said valve means preventing fluid flowin one direction only and others of said valve means preventing fluidflow in the opposite direction only, and other piston means defining aplurality of other chamber means with said first mentioned piston meansand movable into engagement with at least certain of said one-way valvemeans upon the occurrence of predetermined pressure dilferences betweensaid first and other chamber means to prevent fluid flow through saidcertain one-way valve means.

4. The device defined in claim 3 in which said'one-way valve meanscomprise flexible flappers associated with each of said opening definingmeans respectively, said flappers each being of greater area than thearea of the end of the opening associated therewith whereby said flapperprevents fluid flow through said associated opening defining means uponthe occurrence of predetermined pressure differentials on opposite sidesof said reaction means.

5. The device defined in claim 3 in which opening defining means areprovided which communicate one of said other chamber means with one ofsaid first chamber means, said last-mentioned opening defining meansbeing small in comparison with the volume of said chamber means toprovide only restricted communication between said one other chambermeans and said one first chamber means.

6. In a hydraulically operable clutch for mounting upon a rotatableshaft, a housing, piston means respectively at said housing and movabletherewith, a reaction plate in said housing intermediate said pistonmeans and held against axial movement relative to the shaft, saidreaction plate defining a pair of first chamber means with said assemblyadapted generally annular opposite ends of piston means and housing, aplurality of spaced opening defining means extending through saidreaction plate, a plurality of one-way valve means respectively disposedin said opening defining means comprising flexible flappers, meansattaching certain of said flappers to one side of said reaction plateand means attaching other of said flappers to the opposite side of saidreaction plate whereby said one-way valve means are so arranged thatcertain ones thereof prevent fluid flow in one direction only and otherones thereof prevent fluid flow in the opposite direction only, a secondpair of piston means respectively associated with said first mentionedpiston means to define therewith secondary chamber means, said secondpiston means comprising portions movable toward said reaction plate uponthe occurrence of predetermined pressure differences between said firstand secondary chamber means to prevent fluid flow through at leastcertain of said oneway valve means.

7. In a hydraulically operable clutch assembly, a housing, clutch means,spaced piston means movable to engage said clutch means, reaction meansdefiningv a plurality of first chamber means with said piston means andhousing, a plurality of oneway valve means extending between saidplurality of first chamber means, certain of said valve means preventingfluid flow in one direction only and others of said valve meanspreventing fluid flow in the opposite direction only, and other pistonmeans defining in part other chamber means and movable upon theoccurrence of predetermined pressure diiferences between said first andother chamber means to prevent fluid flow through certain of saidone-way valve means.

8. The device defined in claim 7 in which means defining a restrictedopening between said first and other chamber means are provided whichpermit delayed pressure equalization between the chamber means.

References Cited in the file of this patent UNITED STATES PATENTS

